def finish(me):
pass
+class ExpectedError (Exception): pass
+
###--------------------------------------------------------------------------
### A bulk DNS resolver.
+class ResolverFailure (ExpectedError):
+ def __init__(me, host, msg):
+ me.host = host
+ me.msg = msg
+ def __str__(me):
+ return "failed to resolve `%s': %s" % (me.host, me.msg)
+
+class ResolvingHost (object):
+ """
+ A host name which is being looked up by a bulk-resolver instance.
+ """
+
+ def __init__(me, name):
+ """Make a new resolving-host object for the host NAME."""
+ me.name = name
+ me.addr = None
+ me.failure = None
+
+ def setaddr(me, addr):
+ """Add the address ADDR."""
+ me.addr = addr
+
+ def failed(me, msg):
+ """
+ Report that resolution of this host failed, with a human-readable MSG.
+ """
+ me.failure = msg
+
+ def get(me):
+ """Return the resolved address."""
+ if me.failure is not None: raise ResolverFailure(me.name, me.failure)
+ return me.addr
+
class BulkResolver (object):
"""
Resolve a number of DNS names in parallel.
def __init__(me):
"""Initialize the resolver."""
- me._resolvers = {}
me._namemap = {}
-
- def prepare(me, host):
- """Prime the resolver to resolve the name HOST."""
- if host not in me._resolvers:
- me._resolvers[host] = M.SelResolveByName \
- (host,
- lambda name, alias, addr:
- me._resolved(host, addr[0]),
- lambda: me._resolved(host, None))
+ me._noutstand = 0
+
+ def prepare(me, name):
+ """Prime the resolver to resolve the given host NAME."""
+ if name not in me._namemap:
+ me._namemap[name] = host = ResolvingHost(name)
+ host._resolv = M.SelResolveByName(
+ name,
+ lambda cname, alias, addr: me._resolved(host, addr[0]),
+ lambda: me._resolved(host, None))
+ me._noutstand += 1
def run(me):
"""Run the background DNS resolver until it's finished."""
- while me._resolvers:
- M.select()
+ while me._noutstand: M.select()
- def lookup(me, host):
- """
- Fetch the address corresponding to HOST.
- """
- addr = me._namemap[host]
- if addr is None:
- raise KeyError(host)
- return addr
+ def lookup(me, name):
+ """Fetch the address corresponding to the host NAME."""
+ return me._namemap[name].get()
def _resolved(me, host, addr):
"""Callback function: remember that ADDR is the address for HOST."""
- me._namemap[host] = addr
- del me._resolvers[host]
+ if addr is None:
+ host.failed('(unknown failure)')
+ else:
+ host.setaddr(addr)
+ host._resolv = None
+ me._noutstand -= 1
###--------------------------------------------------------------------------
### The configuration parser.
## Match a $[HOST] name resolution reference; group 1 is the HOST.
RX_RESOLVE = RX.compile(r'(?x) \$ \[ ([^]]+) \]')
-class ConfigSyntaxError (Exception):
+class ConfigSyntaxError (ExpectedError):
def __init__(me, fname, lno, msg):
me.fname = fname
me.lno = lno
def _fmt_path(path):
return ' -> '.join(["`%s'" % hop for hop in path])
-class AmbiguousOptionError (Exception):
+class AmbiguousOptionError (ExpectedError):
def __init__(me, key, patha, vala, pathb, valb):
me.key = key
me.patha, me.vala = patha, vala
"path %s yields `%s' but %s yields `%s'" % \
(me.key, _fmt_path(me.patha), me.vala, _fmt_path(me.pathb), me.valb)
-class InheritanceCycleError (Exception):
+class InheritanceCycleError (ExpectedError):
def __init__(me, key, path):
me.key = key
me.path = path
return "Found a cycle %s looking up key `%s'" % \
(_fmt_path(me.path), me.key)
-class MissingSectionException (Exception):
+class MissingSectionException (ExpectedError):
def __init__(me, sec):
- me.key = key
+ me.sec = sec
def __str__(me):
return "Section `%s' not found" % (me.sec)
-class MissingKeyException (Exception):
+class MissingKeyException (ExpectedError):
def __init__(me, sec, key):
me.sec = sec
me.key = key
def __init__(me, name, cp):
"""Initialize a new, empty section with a given NAME and parent CP."""
+
+ ## The cache maps item keys to entries, which consist of a pair of
+ ## objects. There are four possible states for a cache entry:
+ ##
+ ## * missing -- there is no entry at all with this key, so we must
+ ## search for it;
+ ##
+ ## * None, None -- we are actively trying to resolve this key, so if we
+ ## encounter this state, we have found a cycle in the inheritance
+ ## graph;
+ ##
+ ## * None, [] -- we know that this key isn't reachable through any of
+ ## our parents;
+ ##
+ ## * VALUE, PATH -- we know that the key resolves to VALUE, along the
+ ## PATH from us (exclusive) to the defining parent (inclusive).
me.name = name
me._itemmap = dict()
+ me._cache = dict()
me._cp = cp
def _expand(me, string, resolvep):
string)
return string
- def _get(me, key, map = None, path = None):
+ def _parents(me):
+ """Yield this section's parents."""
+ try: names = me._itemmap['@inherit']
+ except KeyError: return
+ for name in names.replace(',', ' ').split():
+ yield me._cp.section(name)
+
+ def _get(me, key, path = None):
"""
Low-level option-fetching method.
Returns None if no value could be found.
"""
- ## If we weren't given a memoization map or path, then we'd better make
- ## one.
- if map is None: map = {}
+ ## If we weren't given a path, then we'd better make one.
if path is None: path = []
## Extend the path to cover us, but remember to remove us again when
path.append(me.name)
try:
- ## If we've been this way before on another pass through then return
- ## the value we found then. If we're still thinking about it then
- ## we've found a cycle.
- try: threadp, value = map[me.name]
+ ## If we've been this way before on another pass through then return the
+ ## value we found then. If we're still thinking about it then we've
+ ## found a cycle.
+ try: v, p = me._cache[key]
except KeyError: pass
else:
- if threadp: raise InheritanceCycleError(key, path[:])
+ if p is None: raise InheritanceCycleError(key, path[:])
+ else: return v, path + p
## See whether the answer is ready waiting for us.
try: v = me._itemmap[key]
except KeyError: pass
- else: return v, path[:]
-
- ## No, apparently, not. Find out our list of parents.
- try:
- parents = [me._cp.section(p) for p in
- me._itemmap['@inherit'].replace(',', ' ').split()]
- except KeyError:
- parents = []
+ else:
+ p = path[:]
+ me._cache[key] = v, []
+ return v, p
## Initially we have no idea.
value = None
- winner = None
+ winner = []
## Go through our parents and ask them what they think.
- map[me.name] = True, None
- for p in parents:
+ me._cache[key] = None, None
+ for p in me._parents():
## See whether we get an answer. If not, keep on going.
- v, pp = p._get(key, map, path)
+ v, pp = p._get(key, path)
if v is None: continue
## If we got an answer, check that it matches any previous ones.
raise AmbiguousOptionError(key, winner, value, pp, v)
## That's the best we could manage.
- map[me.name] = False, value
+ me._cache[key] = value, winner[len(path):]
return value, winner
finally:
## Special handling for the `name' key.
if key == 'name':
value = me._itemmap.get('name', me.name)
+ elif key == '@inherits':
+ try: return me._itemmap['@inherits']
+ except KeyError: raise MissingKeyException(me.name, key)
else:
value, _ = me._get(key)
if value is None:
"""
## Initialize for a depth-first walk of the inheritance graph.
- d = {}
- visited = {}
- stack = [me.name]
+ seen = { 'name': True }
+ visiting = { me.name: True }
+ stack = [me]
## Visit nodes, collecting their keys. Don't believe the values:
## resolving inheritance is too hard to do like this.
while stack:
- sec = me._cp.section(stack.pop())
- if sec.name in visited: continue
- visited[sec.name] = True
+ sec = stack.pop()
+ for p in sec._parents():
+ if p.name not in visiting:
+ stack.append(p); visiting[p.name] = True
- for key, value in sec._itemmap.iteritems():
- if key == '@inherit': stack += value.replace(',', ' ').split()
- else: d[key] = None
+ for key in sec._itemmap.iterkeys(): seen[key] = None
## And we're done.
- return d.iterkeys()
+ return seen.iterkeys()
class MyConfigParser (object):
"""
try: u = sec.get('user')
except MissingKeyException: pass
else: cdb.add('U%s' % u)
- url = M.URLEncode(laxp = True, semip = True)
+ url = M.URLEncode(semip = True)
for key in sorted(sec.items()):
if not key.startswith('@'):
- url.encode(key, ' '.join(M.split(sec.get(key))[0]))
+ url.encode(key, sec.get(key))
cdb.add(label, url.result)
cdb.add('%AUTO', ' '.join(auto))
cdb.finish()
cdb = CDB.cdbmake(opts.cdbfile, opts.cdbfile + '.new')
else:
cdb = CDBFake()
- conf = getconf(args[1:])
- output(conf, cdb)
+ try:
+ conf = getconf(args[1:])
+ output(conf, cdb)
+ except ExpectedError, e:
+ M.moan(str(e))
+ exit(2)
if __name__ == '__main__':
main()
~mdw / tripe / blobdiff